Grinding jig



Feb.- 2, 1943. i J. Y.B| A2EK Erm. 2,309,620

' ,GRINDING JIG Filed Aug. 23, 1940.

JNVENTORS. JOHN Y BL A ZEK @L BERT yEARS ERNo/v oY BY i e@ ATTORNEYS.

Patented Feb. 2, 1943 GRINDING JG John Y. Blazek, Bedford, and Gilbert E. Sears and Vernon R. Roy, Cleveland, Ohio, assignors to Lernpco Products, Inc., Cleveland, Ohio, a corporation of Ohio Application August 23, 1940, serial No. 353,878

3 Claims. (Cl. 51-124) This invention relates generally as indicated to a grinding jig and has reference more specifically to a universal jig for grinding the lining of brake shoes of the type conventionally used in vehicular brakes.

Jigs of the type described heretofore known, includes brake shoe locating means which are separate and independent of brake shoe clamping means and consequently require manipulation and observation of two separate means before a brake shoe can be accurately clamped for grinding. One of the objects of this invention has been to provide unitary or combined brake shoe locating and clamping means.

The brake shoe locating means and the brake shoe clamping means of brake shoe grinders heretofore known either could not quickly and accurately grind a wide variety of sizes of brake shoes or could do so only by virtue of special adaptors. The necessity for special adaptors has been particularly offensive where the brake shoe locating or the brake shoe clamping means have' been arcuate and of such a radius as to engage for a considerable circumferential distance the interior cylindrical surface of a brake shoe. Amother object of this invention has been to provide a device of the character described which will quickly and accurately accommodate a relatively Wide variety of sizes of brake shoes without the necessity of special adaptors.

Brake shoe grinders have heretofore been provided with means for actuating the brake shoe clamping means towards and away from the grinding or abrasive surface, but such means have too frequently or have in certain circumstances been found to actuate the brake shoe clamping means either too rapidly or too slowly. Where such actuation has been too rapidly, irreparable injury is apt to be inflicted upon the brake lining particularly when the operator is not highly skilled. When such actuating means are too slow the long time element involved makes for inefficiency. Another objectof this invention has been to provide means for rapidly or for slowly actuating the brake shoe clamping means towards and away from the abrasive surface.

Still another object of this invention has been' to provide a device of the character described which is. mechanically simple and which can be economically manufactured.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described-and particularly pointed out in the claims; the annexed drawing and the following description setting CTI forth in detail certain structure embodying the invention, such disclosed structure constituting, however, but one of various forms in which the principle of the invention mayl be used.

l In said annexed drawing- Fig. 1 is a plan view of a device having incorporated therein the principal features of this invention;

Fig. 2 is a side elevation of a portion of the device seen in Fig. 1;

Fig. 3 is a section taken Fig. 2; and

Fig. 4 is a plan view of a modification of certain elements seen in Fig. 3. n

With reference now more particularly to the drawing, there will be seen in Fig. 1 and supported by a base I0, an abrasive surface Il provided with a dust guard I3 and suitably driven by a suitable source of power such as an electric motor I2. A plane bearing surface I5 is provided on the base and, for a purpose which will presently appear, is provided with one or more openings !6. The combined or unified brake shoe locating andv clamping means hereinbefore referred to is journalled, preferably rotatably, to this surface and will now be described.

Such combinedV means are Vsupported by a platform 20 provided witha lower plane surface which is journaled to the surface I5. Suitable means are provided for rotating the platform relatively to the base and to this end there is projecting from one of them, preferably the platform, a pin 2| adapted for entering any of the said openings in the surface I5 so that the axis about which the platform pivots relatively to the base may be any of these openings and, depending on the opening selected, the distance between such axis and the abrasive surface is fixed. For facilitating vrotation of the platform a handle 22 is provided.

For the above indicated purpose of moving the brake shoe locating and clamping means towards andv away from the abrasive surface, the platform 20 is provided with a boss 24 which in turn is' provided with a slideway for movably guiding an elongated beam 25, the forward or abrasive surface adjacent end of which supports the brake shoe locating and clamping means.

Such means preferably comprise a pair of brake shoe clamping lower and upper plates 21 and 28, respectively, each provided with a step 29. These plates may be integral or, as is seen in the drawing, may be composite or built up or more than one plate with the forward or abrasive surface adjacent edges of two `of the plates spaced on the lines 3;-3 of from each other so as to provide the said steps. In either event the lower plate or plates 21 may be secured to the forward end of the beam 25 by suitable means such as bolts 3l. The upper and lower plates are similar to each other and, as is seen in Fig. 3, the brake shoe adjacent portions 33 of the plates are preferably relatively straight and if curved are of a radius which is considerably larger than the radius of the largest brake shoe to be ground. These portions sep'- arate a pair of spaced corners or rough jaw surfaces 34 which engage the edges of a brake shoe C at spaced points thereof so that that portion of the brake shoe which is between the corners` is spaced from the portions 33. The inner cylindrical surface C of the brake shoe engages and abuts the riser of the steps 29. The riser of the steps also serves as the brake shoe locating means and for this purpose the portion 35 of the corners of the risers are located on a line, the perpendicular bisector 31 of which passes through the axis about which the platform is adapted for pivoting. Thus the center of the brake shoe lies on this perpendicular bisector and it will be readily seen that if the pin 2| is inserted into one of the said openings so as to properly space the axis of the pin from the abrasive surface a distance equal to the radius of the brake shoe, the original radius of the brake shoe will be reproduced and the lining thereof will be ground to a true cylindrical surface.

For providing relative movement between the plates so as to clamp a brake shoe therebetween, the upper plate moves relatively to the lower plate and has a pair of openings which slidably engage a pair of slideways in the form of cylindrical posts 38, one end of each of which is suitably anchored to the beam 25 and the other endof each of which is suitably secured to a spacer plate 4U. Freely passing through an opening in the plate 28 and also anchored to the beam 25 and secured to the spacer plate 4D is a threaded shaft 42 which is threadedly engaged by a nut 43, the upper surface of which engages the lower surface of the plate 28. Threadingly engaged by the spacer plate 4i) is a hand screw 46, the lower end of which engages the upper surface of the plate 28. Thus it will be Seen upon manipulation of the nut 43 and of the handscrew 46, the plates 21 and 28 will be brought into clamping engagement with the brake shoe C. If desired, suitable springs may be interposed between the plates 21 and 28 for urging them apart. e

The above mentioned means for rapidly or slowly actuating the brake shoe clamping means towards and away from the abrasive surface actuates the beam 25 by means of a rack 50 carried by the beam. This rack is in mesh with a pinion which is enclosed within a housing 52 of the platform and which is actuated by means of a handwheel 53. A boss 55 of the platform 29 is threadingly engaged by a micrometer screw S, the head 51 of which engages one side of a blocl 58 for urging the beam forwardly. For urging the beam rearwardly the micrometer screw is suitably provided with a collar 60 which engages the other side of the block 58. The head 51 and the block 58 are provided `with suitable indicia means 62 which, to any suitable ydegree of graduation, indicates the amount of movement imparted to the block relatively to the boss 55; As is seen in Fig. 2 the beam 25 projects through a recess of the block 58 and is retained in such recess by means of a bottom clamping plate 64 which-is actuated into and out of clamping engagement with the bottom of the beam by suitable means such as screw 65, the latter being provided with a suitable nger lever. Thus, manipulation of the screw 65 clamps or unclamps the beam 25 relatively to the block 58 and renders effective fine or slow micrometer adjustment or actuation of the base towards and away from the abrasive surface. When the screw 65 is in unclamping position, the beam 25 may be rapidly actuated by manipulation of the hand wheel 53. Since the vrack and pinion are responsive to actuation of the screw 56, no means need be provided for rendering the rack and pinion ineffective. In order to maintain the beam 25 locked relatively to the platform, the latter is provided with set screw means lb1 which engages the beam. This locking of the beam relatively to the platform is very desirable where it is desired to reproduce or duplicate a series of brake shoes.

In operation, a brake shoe is placed between 'the steps 29 of the plates 21 and 28 and the hand screw 46 and the nut 43 manipulated until the upper plate is parallel to the lower plate and the treads of the steps of both plates are in clamping engagement with the brake shoe. Due to the guideway posts 38, the four corners of the step 29 will be maintained aligned so that the brake shoe will be properly located. After the brake shoe is clamped between them the set screw means 61 is released and the beam 25 moved forwardly towards lthe abrasive surface by either the fast or the slow feeding means until the brake shoe is almost in engagement with the abrasive surface. The platform is then pivoted about the pin 2| so that the brake shoe is remote from the abrasive surface and the beam 25 is then fed slightly to the right of Fig. 2 by the slow feed means and the set screw means 61 clamps the beam to the platform. The platform is then rotated so as to bring theA entire brake shoe into abrading relation with the abrasive surface. If after a few passes the brake lining is not cleaned up, then the set screw means 61 is released and the beam fed a suitable` small amount towards the abrasive surface by the slow feeding means, whereupon the brake shoe may be given a few more passes. This process is repeated until a satisfactory finish is produced on the brake lining. It is to be noted that regardless of the amount of movement im-V parted to the beam relatively to the platform, unless the pin 2l is inserted into a different hole of the surface I5, one and only one radius will be produced on all shoes.

From the foregoing it will be seen that all brake shoes, the radii of which are smaller than the radii interconnecting the corners 36 of the steps 29, may be located and clamped by a device having incorporated therein the principal features of this invention. It will also be seen that brake shoe locating means, namely the corners 36, and the brake shoe clamping means, namely, the jawsurfaces 34, are so combined that the function of one is tied up with the function of the other and they bear a constant relation toeach other.. "It will further be seen that the`hand wheel 53 rapidly actuates the beam and that the head 51 slowly actuates the beam.

In Fig, 4 there is seen a modification of the plates 21 and 28. Similar reference characters identify similar elements in both the preferred and the modified embodiments and only the differences between the 'embodiments will be described.v The'ch'ief difference is that each of the plates is provided with a second pair of jaw surfaces 14 located relatively to the perpendic.-

ular bisector 31 similarly to the pair of jaw surfaces 34. rIhe jaw surfaces 14 are provided with a step 19 similar to step 29, and portions 16 of the corners of the raiser of step 19 similar to the portions 36 of the raiser of step 29. The corn'ers of the jaw surfaces 14 and portion 16 are sharper and are spaced apart more than are corresponding corners of the jaw surfaces 34 and portions 36. The jaw surfaces 'I4 are separated or spaced by portion 13 which is similar to portion 33. Openings 3la are provided for bolts 3|. Thus, by reversing the plates so as to present the jaw surfaces 14 instead of the jaw surfaces 34, brake shoes of larger diameters may be more accurately located and clamped.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the structure herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim as our invention:

1. In a device of the character described, the combination of a base, an abrasive surface carried thereby, and rotatable means for maintaining a brake shoe in abrading relation with said abrading surface comprising a pair of plates each having a step, each of said steps having spaced corners Which lie on a line the perpendicular bisector of which passes through the axis about which said means rotates, that portion of each of said plates which interconnects the corners thereof being of a relatively large radius of curvature whereby the edges and the inner cylindrical surface of brake shoes of various radii may be located by said corners and clamped between said steps with the center of the brake shoe lying on said perpendicular bisector.

2. In a device of the character described, the combination of a base, an abrasive surface carried thereby, a platform rotatably carried by said base, a pair of brake shoe clamping plates movable relatively to each other, one of said clamping plates being rigidly carried by said platform, a spacer plate disposed to one side of said clamping plates, a slideway projecting from said spacer plate disposed parallel to the axis about which said platform rotates and adapted for slidably engaging the other of said clamping plates, means for exerting a force on said other clamping plate for urging such plate towards said one clamping plate and means for exerting a clamping force on said other clamping plate for urging such plate away from said one clamping plate.

3. The combination of a base, an abrasive element carried thereby, a platform rotatably carried by said base and a beam movably carried by said platform, in combination with a pair of plates for maintaining a brake shoe in abrading relation with said abrasive element, one of said* plates being provided with a pair of spaced steps JoHN Y. BLAZEK. GILBERT E. SEARS. vERNoN R. RoY. 

